Methods using a separation membrane having the selective permeability has been drawn to attention for separating the organic vapor mixture produced by heating and vaporizing a liquid mixture containing organic compounds (the organic vapor separation). The gas separation membrane module used in this method includes plate and frame types, tubular types, hollow fiber types and the like. Among them, the hollow fiber type gas separation membrane module is industrially advantageous and is used extensively because not only it has beneficially the largest area of a membrane per unit volume but also it is excellent in pressure resistance and self-supporting.
The hollow fiber type gas separation membrane modules has the hollow fiber element, wherein at least one end of the fiber bundle consisting of multiple hollow fiber membranes having the selective permeability is fixed and bound together with a plate (tube sheet) of a cured resin of cast molding, and the fiber bundle is housed in a vessel equipped with at least a mixed gas inlet, a permeate gas outlet and a non-permeate gas outlet. Besides it functions to fix the fiber bundle together in a single body, the tube sheet has another function to partition the internal space of the hollow fiber membrane from its external space, and to retain the gas-tightness of the internal space and external space by sealing between the hollow fibers and between the hollow fibers and the vessel. The hollow fiber type gas separation membrane module would fail to perform suitable separation if the gas-tightness by the tube sheet were lost.
The organic vapor separation by using the hollow fiber type gas separation membrane module is carried out as follows. The organic vapor mixture produced by heating and vaporizing a liquid mixture containing organic compounds is supplied to the gas separation membrane module from a feed gas inlet. While the organic vapor mixture flows and contacts the hollow fiber membrane, the permeate vapor that has permeated the hollow fiber membrane is separated from the non-permeate vapor that has not permeated the hollow fiber membrane. The permeate vapor is collected from the permeate gas outlet and the non-permeate vapor is collected from the non-permeate gas outlet. Since the hollow fiber membrane has the selective permeability, the permeate vapor is rich in a component with higher permeability rate (the higher permeable component) and the non-permeate vapor has less such component. As a result, the organic vapor mixture is separated into the permeate vapor rich in the higher permeable component and the non-permeate vapor with less of the higher permeable component.
As the organic vapor separation by using the hollow fiber type gas separation membrane module, for example, the patent document 1 proposes a method for purifying and collecting a high-purity organic compound by dehydrating an aqueous solution containing the organic compound. The aqueous solution containing the organic compound is initially heated and vaporized to produce an organic vapor mixture comprising the vapor of the organic compound and the water vapor, and next the organic vapor mixture is fed to contact one side of the hollow fiber type gas separation membrane (hollow fiber membrane) made from aromatic polyimide at a temperature not lower than 70° C. While organic vapor mixture flows, the water vapor is selectively separated by permeation, whereby the organic vapor mixture with a reduced content of the water vapor is obtained.
The patent document 2 proposes a method for effectively dehydrating a water-organic vapor with a relatively small area. The effective dehydration is achieved by using a gas separation membrane module, in which the circumferential part of the hollow fiber bundle is covered with a film-form substance.
As a resin for cast molding used in the application of the tube sheet for the hollow fiber type gas separation membrane module for organic vapor separation, for example, the patent document 3 discloses the epoxy resin composition containing a tetraglycidyl compound.
As an adhesive for the hollow fiber for the separation membrane used for the separation of an organic solvent by the pervaporation method, for example, the patent document 4 also discloses a bifunctional or trifunctional epoxy resin composition obtained by the reaction with aminophenols and epihalohydrin.
Patent document 1: JP-A-S63-267,415
Patent document 2: JP-A-2000-262,838
Patent document 3: JP-A-H02-31,821
Patent document 4: JP-A-H02-218,714